Add Fake Interior Shader

[orels1]

Fake Interior shaders are a very common approach for creating detail in repetitive buildings, making cityscapes much more interesting.

An interesting approach could be to also add support for double-relief mapping, like in the Matrix Awakening Demo.

One of the requirements for this would also be to add some sort of Baking utility so people can easily create their own layouts

• [x] Add a basic Interior Mapping Shader
• [x] Add Support for custom surface normals for adding water droplets or glass surface patterns to add a refraction effect
• [x] Add support for double-relief mapping
• [ ] Add a baking tool to easily make new fake interior cubemaps and relief textures